The present invention relates to a sub frame structure of a vehicle in which a rear suspension of the vehicle is supported, for example.
In a vehicle, such as an automotive vehicle, a rear suspension connecting a rear wheel and a vehicle body performs a function of pressing the rear wheel against a road surface and another function of a shock absorber to suppress an impact of unevenness of the road surface on the vehicle body. There are various types of rear suspension performing these functions in a suspension mechanism and the like.
Japanese Patent Laid-Open Publication No. 2013-169812, for example, discloses a multi-link type of rear suspension, in which plural arm members are connected to a rear sub frame, the rear sub frame being formed in a parallel crossed shape by a pair of right-and-left side members and front-and-rear cross members which are spaced apart from each other in a vehicle longitudinal direction and interconnect the side members, respectively.
More specifically, the multi-link type of rear suspension disclosed in the above-described patent document is configured such that a front-side lower arm, a rear-side lower arm, and an upper arm, which are respectively coupled to a rear wheel via a knuckle, are connected to the rear sub frame, and a trailing arm, a front end of which is connected to a vehicle body, is connected to the knuckle.
Herein, in the multi-link type of rear suspension like the one disclosed in the above-described patent document, when an input caused by the unevenness of the road surface or the like acts on the rear wheel from a front side of a vehicle, a load is applied to the rear suspension obliquely upward and rearward.
Herein, a vertical load (load acting in a vertical direction) which is part of the above-described upward-and-rearward oblique load is absorbed by a swinging movement of the arm members, such as the front-side lower arm, and a biasing force of a suspension spring. Meanwhile, a longitudinal load (load acting in the vehicle longitudinal direction) is transmitted to the rear sub frame through the front-side lower arm and the rear-side lower arm and also transmitted to the vehicle body through the trailing arm.
Therefore, in a case in which the trailing arm of the above-described multi-link type of rear suspension of the patent document is omitted, for example, the longitudinal load transmitted to the rear sub frame through the front-side lower arm and the rear-side lower arm may increase.
In this case, there is a problem that the above-described increase of the longitudinal load may improperly cause damage of the arm member, improper deformation of a bracket for attaching the arm member, or twisting of the side member.